U.S. patent number 7,284,862 [Application Number 10/988,064] was granted by the patent office on 2007-10-23 for ophthalmic adaptive-optics device with a fast eye tracker and a slow deformable mirror.
This patent grant is currently assigned to MD Lasers & Instruments, Inc.. Invention is credited to Ming Lai, Mei Juan Yuan.
United States Patent |
7,284,862 |
Lai , et al. |
October 23, 2007 |
Ophthalmic adaptive-optics device with a fast eye tracker and a
slow deformable mirror
Abstract
The present invention contemplates to employ an eye-tracking
device in an ophthalmic adaptive-optics system such that slow
wavefront sensor and aberration-compensating element can be
sufficient for the application. The present invention further
contemplates to implement with the eye-tracking device a
motion-compensating mechanism into the system such that the pupil
images on both the wavefront sensor and the aberration-compensating
element remain stationary during the operation of the system.
Inventors: |
Lai; Ming (Webster, NY),
Yuan; Mei Juan (Webster, NY) |
Assignee: |
MD Lasers & Instruments,
Inc. (Pleasanton, CA)
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Family
ID: |
38606954 |
Appl.
No.: |
10/988,064 |
Filed: |
November 13, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60520374 |
Nov 13, 2003 |
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Current U.S.
Class: |
351/209;
351/211 |
Current CPC
Class: |
A61F
9/008 (20130101); A61B 3/14 (20130101); A61F
2009/00846 (20130101); A61F 2009/00872 (20130101); A61F
2009/0088 (20130101) |
Current International
Class: |
A61B
3/14 (20060101); A61B 3/10 (20060101) |
Field of
Search: |
;351/209,210 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schwartz; Jordan M.
Parent Case Text
This application claims the benefit of U.S. Provisional Application
No. 60/520,374, filed on Nov. 13, 2003.
Claims
What is claimed is:
1. An ophthalmic adaptive-optics instrument comprising: an
observation target disposed for a subject eye to fixate; an
aberration-compensating element disposed in the observation path of
said subject eye and receiving a pupil image through relay optics,
wherein said aberration-compensating element is driven by a control
signal and is capable to compensate low and high order aberration
of said subject eye; a wavefront-sensing device sensing the
aberration of said subject eye via said aberration-compensating
element; control electronics coupled to said wavefront-sensing
device to generate said control signal to drive said
aberration-compensating element; an eye motion-sensing device
sensing the movement of said subject eye; and a motion-compensating
mechanism coupled to said eye motion-sensing device and disposed to
compensate said movement of said subject eye, such that said pupil
image stays stationary with respect to said aberration-compensating
element; wherein said aberration-compensating element compensates
said aberration of said subject eye while said motion-compensating
mechanism compensates said movement of said subject eye.
2. An ophthalmic adaptive-optics instrument of claim 1, further
comprising: a retina camera disposed to image the retina of said
subject eye via said aberration-compensating element and said
motion-compensating mechanism; wherein said ophthalmic
adaptive-optics instrument is for retina imaging.
3. An ophthalmic adaptive-optics instrument of claim 1, further
comprising: a con-focal scanning laser ophthalscope disposed to
image the fundus of said subject eye via said
aberration-compensating element and said motion-compensating
mechanism; wherein said ophthalmic adaptive-optics instrument is
for con-focal scanning laser tomography.
4. An ophthalmic adaptive-optics instrument of claim 1, wherein
said observation target is an illuminated starburst target.
5. An ophthalmic adaptive-optics instrument of claim 1, wherein
said aberration-compensating element is a deformable mirror.
6. An ophthalmic adaptive-optics instrument of claim 1, wherein
said aberration-compensating element consists of a deformable
mirror and a set of compensation lenses.
7. An ophthalmic adaptive-optics instrument of claim 1, wherein
said aberration-compensating element is a spatial phase
modulator.
8. An ophthalmic adaptive-optics instrument of claim 1, wherein
said aberration-compensating element has a response time longer
than 100 ms.
9. An ophthalmic adaptive-optics instrument of claim 1, wherein
said wavefront-sensing device is a Hartmann-Shack wavefront
sensor.
10. An ophthalmic adaptive-optics instrument of claim 1, wherein
said wavefront-sensing device has a data acquisition time longer
than 100 ms.
11. An ophthalmic adaptive-optics instrument of claim 1, wherein
said eye motion-sensing device is a camera based tracking
device.
12. An ophthalmic adaptive-optics instrument of claim 1, wherein
said eye motion-sensing device is a pupil tracking device employing
x-y scanning beams.
13. An ophthalmic adaptive-optics instrument of claim 1, wherein
said eye motion-sensing device has a sensing rate of 30 Hz or
higher.
14. A method for constructing an ophthalmic adaptive-optics
instrument, comprising the steps of: providing an observation
target for a subject eye to fixate; providing an
aberration-compensating element disposed in the observation path of
said subject eye and receiving a pupil image through relay optics,
wherein said aberration-compensating element is driven by a control
signal and is capable to compensate low and high order aberration
of said subject eye; providing a wavefront-sensing device to sense
the aberration of said subject eye via said aberration-compensating
element; providing control electronics coupled to said
wavefront-sensing device; generating said control signal to drive
said aberration-compensating element to compensate said aberration
measured by said wavefront-sensing device; providing an eye
motion-sensing device sensing the movement of said subject eye; and
providing a motion-compensating mechanism coupled to said eye
motion-sensing device and disposed to compensate said movement of
said subject eye, such that said pupil image stays stationary with
respect to said aberration-compensating element; wherein said
aberration-compensating element compensates said aberration of said
subject eye while said motion-compensating mechanism compensates
said movement of said subject eye.
15. A method of claim 14, further comprising steps of: providing a
retina camera disposed to image the retina of said subject eye via
said aberration-compensating element and said motion-compensating
mechanism; wherein said ophthalmic adaptive-optics instrument is
for retina imaging.
16. A method of claim 14, further comprising steps of: providing a
con-focal scanning laser ophthalscope disposed to image the fundus
of said subject eye via said aberration-compensating element and
said motion-compensating mechanism; wherein said ophthalmic
adaptive-optics instrument is for con-focal scanning laser
tomography.
17. An ophthalmic adaptive-optics instrument comprising: an
observation target disposed for a subject eye to fixate; an
aberration-compensating element disposed in the observation path of
said subject eye and receiving a pupil image through relay optics,
wherein said aberration-compensating element is driven by a control
signal and is capable to compensate low and high order aberration
of said subject eye; an eye motion-sensing device sensing the
movement of said subject eye; a motion-compensating mechanism
coupled to said eye motion-sensing device and disposed in said
observation path of said subject eye, such that said pupil image
remains stationary with respect to said aberration-compensating
element; a wavefront-sensing device sensing the aberration of said
subject eye via said motion-compensating mechanism and said
aberration-compensating element; and control electronics coupled to
said wavefront-sensing device to generate said control signal to
drive said aberration-compensating element; wherein said
aberration-compensating element compensates said aberration of said
subject eye, while said motion-compensating mechanism compensates
said movement of said subject eye.
18. An ophthalmic adaptive-optics instrument of claim 17, wherein
said motion-compensating mechanism includes two pairs of folding
mirrors.
19. An ophthalmic adaptive-optics instrument of claim 17, wherein
said motion-compensating mechanism includes two folding mirrors
moveable to compensate for horizontal and vertical displacements
respectively.
20. An ophthalmic adaptive-optics instrument of claim 17, wherein
said motion-compensating mechanism has a response time of 30 ms or
shorter.
Description
FIELD OF THE INVENTION
The present invention relates to method and apparatus for
constructing an adaptive optics instrument for ophthalmic
applications. In particular, the present invention relates to
method and apparatus for constructing an ophthalmic adaptive optics
instrument with a fast eye tracker and a slow deformable
mirror.
BACKGROUND OF THE INVENTION
Theory and experiments have demonstrated that adaptive optics can
benefit many ophthalmic applications, such as improving the
resolution of retina camera, improving the resolution of con-focal
scanning laser tomography of the human fundus, and verifying
surgical outcome prior a refractive laser surgery. To implement
adaptive optics into these applications, a wavefront sensor and an
aberration-compensating element are necessary to integrate into an
ophthalmic instrument. The wavefront sensor is used to sense all
optical aberrations of the eye and the aberration compensating
element, e.g. a deformable mirror, is used to compensate these
aberrations to make the eye a better optical imaging system.
For ophthalmic application of adaptive optics, the aberration of
the eye is relatively stable while the eye itself may move rapidly.
In a typical prior art ophthalmic adaptive optics system, both the
wavefront sensor and the aberration-compensating element need to
have a response time short enough to accommodate the eye movement.
A characteristic eye movement can happen within a time interval of
5 ms to 100 ms. To make the wavefront sensor and the
aberration-compensating element to response in such a time scale is
found both challenging and expensive.
SUMMARY OF THE INVENTION
The present invention recognizes the difficulty with the prior art
ophthalmic adaptive optics system and contemplates to employ an
eye-tracking device to the system such that slow wavefront sensor
and aberration-compensating element can be sufficient for the
application. The present invention further contemplates to
implement with the eye-tracking device a motion-compensating
mechanism into the system such that the pupil images on both the
wavefront sensor and the aberration-compensating element remain
stationary during the operation of the system. One direct
application of such an ophthalmic adaptive optics system is to
provide patient-verified prescription of high order aberration for
customized refractive surgery, as described in a pending
application entitled method and apparatus for obtaining
patient-verified prescription of high order aberration.
In one embodiment of the present invention, an ophthalmic
adaptive-optics instrument is implemented with an observation
target, a deformable mirror, a wavefront sensor, and an
eye-tracking device. The eye-tracking device includes a sensing
mechanism to sense the eye motion and a motion-compensating
mechanism to compensate the eye motion. The instrument enables the
patient to look at the observation target via the deformable mirror
and the motion-compensating mechanism. The wavefront sensor senses
the eye aberration also via the deformable mirror and the
motion-compensating mechanism. The pupil image is relayed onto the
deformable mirror and the wavefront sensor via the
motion-compensating mechanism and thus remains constant at the
deformable mirror regardless any eye movement. The wavefront sensor
and the deformable mirror can, therefore, make aberration
measurement and compensation within a time interval not limited by
the eye movement.
Accordingly, an objective of the present invention is to provide a
new and improved method and apparatus for an ophthalmic adaptive
optics instrument.
Another objective of the present invention is to provide an
ophthalmic adaptive-optics instrument with a fast eye tracker and a
slow wavefront sensor and/or a slow aberration-compensating
element.
A further objective of the present invention is to enable the use
of slow deformable mirror for ophthalmic adaptive-optics
applications.
The above and other objectives and advantages of the present
invention will become more apparent in the following drawings,
detailed description, and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows schematically an ophthalmic adaptive-optics instrument
employing an eye-motion compensating mechanism.
FIG. 2 shows schematically a motion-compensating mechanism to
compensate eye movement.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 shows schematically an ophthalmic adaptive-optics instrument
100 employing an eye-motion compensating mechanism 70, in
accordance with the present invention. The ophthalmic
adaptive-optics instrument 100 consists of relay optics 20, a
deformable mirror 21, a wavefront sensor 22, an observation target
23, a control electronics 50, an eye motion sensing device 40, and
a motion compensating mechanism 70.
The relay optics 20 relays the wavefront of an outgoing beam 27
from the pupil plane to the deformable mirror 21. The relay optics
20 comprises two or more lenses with all their own high order
aberration well balanced and minimized. The relay optics 20 may
include a set of compensation lenses or other mechanism to
compensate low order aberration of the subject eye, such as
defocusing and regular astigmatism. The construction and alignment
of relay optics 20 are known to those skilled in the art.
The deformable mirror 21 is used here as an aberration-compensating
element to modify or compensate wavefront distortion of a light
beam impinging on it. The deformable mirror 21 is an
adaptive-optics element and, driven by a programmable control
signal 51, it can produce a position-dependent phase modulation
across the beam. Therefore, the deformable mirror 21 works as a
spatial phase modulator and can be replaced by other type of
spatial phase modulators. The construction and control algorithm of
a deformable mirror are known to those skilled in the art.
The wavefront sensor 22 projects a probe beam 24/26 into a subject
eye 60 via the deformable mirror 21. The scattered light from the
eye retina forms an outgoing beam 27 from the eye 60. This outgoing
beam 27 passes through the deformable mirror 21 and turns into beam
28. The wavefront of the beam 28 is then measured with the
wavefront sensor 22. The wavefront sensor 22 produces an output
signal 29 indicating the aberration of the beam 28. The wavefront
sensor 22 can be a Hartmann-Shack device. The construction and
alignment of wavefront sensor 22 are known to those skilled in the
art.
The observation target 23 is for the patient to fixate. It can have
an illuminated starburst pattern or other patterns commonly used in
ophthalmic instruments. The structure and alignment of observation
target are known to those skilled in the art.
The control electronics 50 reads in the signal 29 and generates a
control signal 51 to drive the deformable mirror 21. The deformable
mirror 21 thus modifies and compensates the aberration of the
subject eye 60 according to the control signal 51.
The eye motion-sensing device 40 is used to measure and monitor eye
movement. The eye motion-sensing device 40 can be a camera based
tracking device or a pupil-tracking device with x-y scanning beams.
To be effective for the present application of ophthalmic
adaptive-optics instrument, the sensing device 40 shall have a
sensing rate 30 Hz or higher. The construction and alignment of the
eye motion-sensing device 40 are known to those skilled in the
art.
The motion-compensating mechanism 70 is disposed in the optical
path between the subject eye 60 and the deformable mirror 21. The
motion-compensating mechanism 70 is driven by the eye
motion-sensing device 40 to compensate the eye movement such that
the pupil image on the deformable mirror 21 remains constant during
the operation of the instrument. One design of a
motion-compensating mechanism 70 is depicted in FIG. 2. Many
designs of motion-compensating mechanism are known to those skilled
in the art.
In operation, the patient's eye 60 looks at the observation target
23 through the deformable mirror 21 and the motion-compensating
mechanism 70. The eye motion-sensing device 40 constantly senses
the eye movement and drives the motion-compensating mechanism 70 to
compensate the eye movement. The wavefront-sensing device 22
detects the wavefront aberration of the eye 60 via the deformable
mirror 21 and the motion-compensating mechanism 70. The control
electronics 50 is then to drive the deformable mirror 21 to make
the measured wavefront aberration toward zero. As a result, the
subject eye 60 can view the observation target 23 more sharply and
clearly with the eye's aberration compensated.
As the eye movement is compensated by the movement-compensating
mechanism 70, the pupil image on the deformable mirror 21, as well
as on the wavefront-sensing device 22, is stationary. The wavefront
measurement and the aberration compensation can thus be made within
a time scale not limited to the eye movement. Practically, it is
difficult to make accurate wavefront measurement and/or aberration
compensation within 100 ms. With the implement of the eye
motion-sensing device 40 and the motion-compensating mechanism 70,
it becomes feasible to adapt a data acquisition time of wavefront
sensing device 22 and a response time of deformable mirror 21 to be
100 ms or longer.
In the above embodiment of the present invention, the ophthalmic
adaptive-optics instrument 100 is simply for a subject eye 60 to
view an observation target 23 through an aberration compensating
element, i.e. the deformable mirror 21. In application as a retina
camera, the ophthalmic adaptive-optics instrument 100 shall include
a retina camera viewing the subject retina through the deformable
mirror 21. In application for con-focal scanning laser tomography,
the ophthalmic adaptive-optics instrument 100 shall include a
con-focal scanning laser ophthalscope viewing the subject fundus
through the deformable mirror 21. The construction and alignment of
retina camera or con-focal scanning laser ophthalscope are known to
those skilled in the art.
FIG. 2 shows schematically a motion-compensating mechanism 70 to
compensate for eye movement. The motion-compensating mechanism 70
consists of four turning mirrors 71, 72, 73 and 74. As shown in the
figure, the mirrors 71 and 72 are arranged to make a vertical shift
of the incoming beam 75, while mirrors 73 and 74 are arranged to
make a horizontal shift of the incoming beam 75. The amount and
sign of vertical shift can be changed through moving mirror 71
along its normal line. Similarly, the amount and sign of horizontal
shift can be changed through moving mirror 73 along its normal
line.
There shall be a driving mechanism to move each of mirror 71 and
mirror 73. The driving mechanism, which is not shown in the figure,
can be made with a translation stage driven by a step motor. The
outgoing beam 76 can thus be shifted corresponding to the eye
movement sensed by the eye motion-sensing device 40. To be
effective for the application of the ophthalmic adaptive-optics
instrument, the motion-compensating mechanism 70 shall have a
response time of 30 ms or shorter.
Although the above description is based on preferred embodiments,
various modifications can be made without departing from the scopes
of the appended claims.
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